When you BRRRR with a partner, the normal end game is you’re splitting the rent 50/50 having put no skin in the game. 

But as time goes on, the “cash flow” allocation will change naturally by itself and I wouldn’t try to control it.

I have just never heard of a situation of this nature.

above the current rent because of the short term nature of the lease. 

You are brokering between two sides for a fee and you have no skin in the game.

We acknowledge the issue either through phone or e-mail (however they contact us) ASAP, but do not run out to handle any issue right then and there unless it is urgent in nature. 

Also, there is always a possibility of the risks from natural disasters, but those no one can foresee.

You either have a buyer's agent representing you (for free) or you have the listing agent representing both sides (but probably representing the seller more... its human nature). 

I definitely learned not to let a so called handyman do ANY repairs while living there after he hit the natural gasoline with a sawzall and moved...

Get a couple more quotes, plus compare material prices with some suppliers in the area  It’s hard to determine whether the price is fair because the nature of the project and the sizes are unknown.